The present invention pertains to network internet protocol and more particularly to a header compression arrangement for wireless network applications.
A prior art method of sending sequencing and timing information to support real time services in internet protocol (IP) networks is by use of the real time protocol (RTP). Network transport for voice is provided by UDP (User Data Protocol) protocol. Wireless IP network applications use vocoded voice. Each vocoded frame is typically 10 to 20 bytes in length of information. The combined RTP/UDP/IP header that is therefore required to be attached to the packet so that the voice frame can reach its destination has a length of about 40 bytes.
The 40 byte combined header is considerable overhead with respect to about 20 bytes of actual voice information for typical wireless vocoder. Sending the combination of 40 bytes of header information with 20 bytes of voice information constitutes an inefficient use of a radio frequency (RF) link.
One approach to the overhead problem is to pack several voice frames together with a single header to improve RF transmission efficiency. However, this approach increases the voice delay significantly. For example, in a CDMA 2000 network, each additional voice frame increases the end to end delay by approximately 60 milliseconds. This produces an unacceptable voice quality.
Voice quality may be further sacrificed to gain bandwidth by using lower bit-rate modes of the vocoder. Again, this is an undesirable situation.
Another approach to the overhead problem is header compression. Available header compression mechanisms are typically designed for generic data compression. Such generic data compression does not take advantage of the peculiar characteristics of voice over packet data. As a result, such header compression techniques perform sub optimally.
Accordingly, it would be highly desirable to have a header compression arrangement for a wireless IP network which makes efficient use of the RF link while providing high quality voice data throughout the network.